Fair Value Measurements - Reconciliation of Assets and Liabilities Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation
Derivative assets	$ 3,137		$ 3,137		$ 1,655
Derivative liabilities	1,118		1,118		$ 741
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	767	$ 1,085	1,023	$ 991
Included in earnings	(38)	(131)	(349)	(370)
Purchases/originations/acquisitions	55	41	190	385
Settlements	(64)	(35)	(173)	(71)
Transfers into Level 3	10	3	39	28
Ending balance	730	963	730	963
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	37	(118)	(264)	(368)
Interest rate contracts \| Level 3
Fair Value Assets Measured On Recurring Basis Unobservable Input Reconciliation
Derivative assets		24		24
Derivative liabilities		9		9
Residential Mortgage Loans
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	185	192	183	179
Included in earnings	0	0	2	(1)
Purchases/originations/acquisitions	0	0	0	0
Settlements	(21)	(11)	(50)	(22)
Transfers into Level 3	10	3	39	28
Ending balance	174	184	174	184
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	0	0	2	(1)
Servicing Rights
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	676	1,039	993	938
Included in earnings	(71)	(171)	(519)	(416)
Purchases/originations/acquisitions	55	42	186	388
Settlements	0	0	0	0
Transfers into Level 3	0	0	0	0
Ending balance	660	910	660	910
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	(2)	(131)	(281)	(329)
Interest rate contracts
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	89	5	10	(1)
Included in earnings	55	51	241	110
Purchases/originations/acquisitions	0	(1)	4	(3)
Settlements	(60)	(40)	(171)	(91)
Transfers into Level 3	0	0	0	0
Ending balance	84	15	84	15
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	61	24	88	25
Equity Derivatives
Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation
Beginning balance	(183)	(151)	(163)	(125)
Included in earnings	(22)	(11)	(73)	(63)
Purchases/originations/acquisitions	0	0	0	0
Settlements	17	16	48	42
Transfers into Level 3	0	0	0	0
Ending balance	(188)	(146)	(188)	(146)
The amount of total gains or losses for the period included in earnings attributable to the change in unrealized gains or losses relating to assets still held	$ (22)	$ (11)	$ (73)	$ (63)

Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Amount of unrealized gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3) and still held.

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Amount of gain (loss) recognized in income from asset measured at fair value on recurring basis using unobservable input (level 3).

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